The Discovery of Radioactivity

After reading this section, you will be able to do the following:

  • Explain radioactive elements and fluorescent minerals.
  • Predict what role radioactive elements and fluorescent minerals play in the discovery of radioactivity.

How was radioactivity discovered?

The discovery of radioactivity, in general, actually came about on a few different fronts. First was the discovery of X-ray radiation that was artificially generated in a laboratory, followed by the discovery of several elements that naturally emit radiation when the nucleus of the atoms disintegrate or decay. These are the elements that today are called radioactive elements and are said to have unstable nuclei.

Just before the turn of the century, in the mid to late 1890's, several scientists were working with cathode ray tubes investigating properties of fluorescent minerals. Fluorescent minerals are certain minerals that glow when exposed to sunlight. At the same time, other scientists were busy gathering evidence on the theory that the atom could be divided into even smaller subatomic particles. Some of this new evidence showed that certain types of atoms disintegrate by themselves.

In the following three sub-units you will learn about the discovery of X-ray, the discovery of radioactive elements, and you will find out who the Curies were and what contribution to science they made.


  1. When the nucleus of an element decays or disintegrates radiation is emitted, and this kind of element is called a radioactive element.
  2. Minerals that glow when sunlight is exposed on them are called fluorescent minerals.